Method of assembling rubber filaments into thread



Feb. 3, 1942. 2,271,865

-'METH0D oF AssEMBLING RUBBER FILAMENTS INT0 THREAD' R. G. JAMES Erm? Filed May l0, 1938 Patented Feb. 3, 1942 METHOD F ASSEIWBLING RUBBER FILAMENTS INTO THREAD Robert Gilbert James and Sydney Frederick Smith, Wylde Green, Birmingham, England,

assignors to Dunlop Rubber Company Limited, London, England, a British company Application May 10, 1938, Serial No. 206,999

In Great Britain July 16, 1937 8 Claims.

Our invention relates to a process for assembling a number, preferably three or more, of rubber laments such as filaments formed by the coagulation of rubber latex into a compact, untwisted thread. l

Multi-filament rubber thread has been found to be particularly useful as compared with sin-- gle filament thread, for example,'in the production of elastic garments because, in a sewing machine, such thread is not torn or cut so readily as a single thread.` For this vpurpose it is desirable that the thread shall be compact and uniform in cross section and that the several filaments of the thread shall adhere to each other with a limited adherence sufficient to prevent their separation in use, but not too great as to destroy the independence of the filaments when the thread is pierced by a sewing needle. Heretofore it has not been possible to attain these desired conditions because it was diiiicult, if not impossible, to ensure the grouping of the filaments in a compact strand with the proper degree of adhesion. For example, in a three-filament thread, the formation of flat, ribbon-like grouping or right angle grouping of the thread could not be ensured.

In our invention separate freshly formed rubber filaments such as formed, for example, by the extrusion of latex into a coagulant or setting agent are drawn separately over a feeding roller or equivalent feeding device, then twisted as a group into a thread and then drawn over a second roller orl conveyor means preferably moving at a higher linear or surface speed. As the several filaments are twisted together they are brought into close, intimate contact with each other, the .more so with an increased number of twists. As the thread thus formed is drawn further, succeeding lengths of the filaments pass into the twisted formation and, as the twisting is not continuous but only for alimited number of twists, this causes an untwisting of the fibers after they have passed the place or zone of twisting, this untwisting being facilitated by the tension applied 'by the second roller to the thread, and also by the fact that there are-only a limited number of twists through which the filaments pass. Accordingly, the filament as it is formed `and coagulated passes first through a twisting zone in which it not `only is brought into forcible surface contact with other filaments but also in` a most compact arrangement, and then is drawn out of the twist while still retaining the .compact formation and the surface contact imposed during the twisting. For example, in a three-fla I formation, and

ment thread each of the three filaments enters into the twist, thereby taking a trefoil assembly in cross section and then untwists while still retaining this assembly. The result is a trefoil thread without twist.

The number of turns to be given in twisting thel group of three or more filaments will be selected in accordance with the speed of travel of the individual filaments, ,the relative surface speeds of the roller, the physical condition of the filaments and the degree of adherence'desired between the several filaments in the completed thread. The twisting may be done by hand or by any suitable tool or machinery, it being understood that once the twisting is given andthe rollers begin rotating, no further twisting is required. Usually, it is sufficient to give a group of three filaments 11/2 rturns or, preferably, a minimum of 2 turns. Generally, it is desirable not to give such a group of filaments more than v 5 or 6 turns. By momentarily pressing and twisting together by hand, or other means, the three or more filament-portions twists o fv opposite directions are imposed on the filaments between the hand, or other means, and the first and second rollers, respectively. On allowing the filaments to proceed, the twist between the hand and the second roller passes over this roller leaving the thread between the rollers twisted in one direction only. This twist is gradually reduced by the continued passage of the thread until about one and a half twists remain in the thread between the rollers, when a condition of equilibrium is reached. The number of turns may, of f fl' course, be adjusted to different conditions, but ordinarily 11/2 twists are required to prevent the untwisting of the filaments as they pass through the second roller.

'I'he various features of the invention are illustrated by way of example in the accompanying drawing, i'n which- Fig. 1 'is a perspective view, partly in section,

of an apparatus for forming the filaments by extrusion of latex and drawing them into thread Fig. 2 is a cross section on a much larger scale i of the formed thread taken on line 2-2 of Fig. 1.

In the accompanying drawing, latex or an y aqueous rubber dispersion is supplied through a pipe I0 to an extrusion head II having a number of extruding orifices I2 that open upwardly in a bath I3 of coagulating or setting liquid. As the fine streams of latex are extruded through the openings or orifices I2 they begin to coagulate to coherent filaments Il which are then drawn composed of a large numbei` of filaments.

upwardly from the surface of the coagulant bath and separately over a roller I4. After passing the roller I5, the filaments are twisted together as at I6 and then pass over a second roller I'I. The arrangement of the rollers is merely conventional, and they may be driven from any suitable source as from a motor I8 and belt I9. The roller I1 is preferably driven at a higher speed than the roller I and, in the diagrammatic sketch of Fig. 1, it is therefore provided with a pulley 20 which drives a larger pulley 2| on the shaft of the roller I5 through a suitable belt 22, this being merely a diagrammatic illustration of the relative speeds of the rollers.

As shown in Fig. 1, the filaments pass through the twist I6 and then gradually untwist by retaining a trefoil formation as indicated in Fig. 2 as they pass over the roller I'I.

For example, when three such filaments are momentarily pressed and twisted together five or six times and then allowed to proceed over the second roller onto a pick-up means, the twist imparted to the filaments is gradually reduced and shortly becomes one complete turn so long as working conditions remain constant. After the continuously renewed filament portions in the vicinity of the second roller have reached this stable configuration, the filaments pass to the second roller in the desired trefoil configuration.

The degree of adhesion between the individual filaments in the multi-filament thread produced according to the method of the present invention can be easily controlled by giving the filaments a regulated amount of drying prior to their unification into a multi-filament formation, for eX- ample, the individual filaments can be dried to the desired degree prior to their reaching the first roller hereinbefore mentioned. For this purpose a drying chamber, such as the drying chamber 23, may be placed between the roller I5 and the roller I 1, specifically between the roller I5 and the' twist I6 as indicated in Fig. 1. l

Again, if desired, the individual filaments after initial coagulation may be passed directly on to the two rollers so as to be formed into a multifilament thread and then, if necessary, further coagulated, washed, stretched, dried or otherwise further treated.

The multi-filament thread may be produced at any` suitable stage as, forinstance, the individual filaments may be coagulated, washed and stretched with or without further washing, partially dried and then converted into multi-filament thread according to the invention.

The multi-filament thread maybe stretched to reduce its general cross-section and, if desired, the multi-filament thread produced, or other multi-filament thread, may be used to produce according to the invention, multi-filament thread In the same manner, single filament and multi-filament threads may beV combined according to the invention to produce thread of a large number of filaments. It is not necessary for the individual filaments to be united to be of the same crosssection or gauge, neither need they be of the same color or even of the same type of compound. The individual filaments may be of different colors for ornamental or identification purposes.

The term latex is used to designate broadly aqueous dispersions of or containing rubber, gutta-percha, balata or similar Vegetable resins occurring naturally, or artificially obtained.

Such artificial aqueous dispersions may include those of coagulated rubber, vulcanized rubber. synthetic rubber, waste or reclaim. Aqueous dis- ,persions of vulcanized latices can also be employed. If desired, any of the aforementioned dispersions may be used alone or in admixture with one another.

Any of the aforesaid dispersions may contain the usual known compounding ingredients and/or may be in concentrated form. Y

Concentrates such as are obtained in United States Patent No. 1,846,164, or British Patents Nos. 290,313 and 219, 635, to which may be added any one or more of the usual compounding ingredients may also be used.

The aqueous dispersions may be made heatsensitive by methods well known in the art.

The term coagulant is used to designate broadly liquid media which bring about solidification of rubber latex by coagulation, or gelling, or by dehydration and coagulation.

What we claim is- 1. A method of forming an assembly of independent filaments adhering to each other at limited surfaces of contact which comprises moving a group of separate filaments having adhesive surfaces lengthwise at equal speeds, twisting said moving filaments to bring them into close but limited contact and then drawing said group of filaments into Contact with and beyond a surface with sufficient tension against said surface to cause said group to untwist without separating whereby said group of filaments leave said surface without substantial twist and with the surfaces of said filaments in adherent contact.

2. The method of claim 1 in which said filaments are freshly coagulated latex rubber.

3. The method of claim 1 in which said filaments are freshly coagulated latex rubber and in which said filaments are subjected to drying before twisting.

4. A method of forming an assembly of independent filaments of rubber composition into a group of independent filaments adhering to each other at limited surfaces of contact which comprises .forming rubber filaments individually at a common speed by continuously extruding an aqueous dispersion of rubber materials into a liquid setting agent, moving the resulting separate filaments lengthwise at equal speeds, twisting said moving filaments while their surfaces are adhesiveto bring them into close but limited Contact and-then drawing said group of filaments Y into contact with and beyond a surface with suficient tension against said surface to cause said group to untwist without separating whereby said group of filaments leave said surface without substantial twist and with the surfaces of said laments in adherent contact.

5.A method of forming an assembly of independent filaments adhering to each other at limy ited surfaces of contact which comprises twisting a group of filaments into a close but limited con-` t tact While their surfaces are sufiiciently adhesive to adhere upon said contact and while said filaments are moving lengthwise at equal speeds and then drawing said group of filaments to contact with a surface moving at a speed greater than the movement of said filaments to said surface and thence beyond said surface to untwist said group without separating the filaments whereby said filaments adhere to each other atl their surface of contact without substantial twist.

6. A method of forming an assembly of independent filaments adhering to each other at limited surfaces of contact which comprises .-moving pendent laments adhering to each other at limited surfaces of contact which comprises moving a group of separate filaments having adhesive surfaces lengthwise at equal speeds, twisting said moving filaments to bring them into clpse but of filaments leave said surface without substantial twist and with the surfaces of said'filaments gia limited contact and then 'drawing said group of v filaments into contact with and beyond a surface rotating in the direction of movement of said group of filaments and at a linear speed greater than that of the 'movement of said group of filaments toward said surface and with sufcient tension against said surface to cause said group to untwist without separating whereby said group in adherent contact.

8. A method of forming an assembly of independent filaments of rubber composition into a group of independent filaments adhering to each other at limited surfaces of contact which ccmprises forming rubber filaments individually at a common speed by continuously extruding an aqueous dispersion of rubber materials into a liquid setting agent, moving the resulting separate filaments lengthwise at equal speeds, twisting said moving filaments while their surfaces are adhesive to bring them into close but limited contact and then drawing said group of filaments into contact with and beyond a surface rotating in the direction and movement of said group of filaments and at a linear speed higher than the movement of said filaments to 4said surface and with sufficient tension against said vsurface to cause said group to untwist Without separating whereby said group of filaments leave said surface Without substantial twist and with the surfaces ofsaid filaments in adherent contact. ROBERT GILBERT JAMES. SYDNEY FREDERICK SMITH. 

